1. Technical Field
The invention relates to a fixing member, a fixing device and an image forming apparatus.
2. Related Art
When an image is formed by an electrophotographic system, a crease of a recording paper sheet having an image formed thereon may occur due to a fixing device equipped with at least a pair of fixing members placed in an image forming apparatus and positioned to be opposite to each other so as to form a contact portion thereof. In order to prevent this paper crease, various methods have been proposed.
In a case of a fixing device using rolls as fixing members, for example, a method is known in which the fixing roll has such a shape that the outer diameter in the axial direction is bigger when the position thereof is closer to the both ends of the fixing member, while it is smaller when the position thereof is closer to the center of the fixing member, (hereinafter, this shape may be referred to as “flare shape”).
In the above method, the speed of delivering a recording paper sheet at the edge part of the recording paper sheet becomes higher than that at the center of the paper sheet, when the recording paper sheet is delivered by rotation of the fixing rolls. Accordingly, the recording paper sheet is delivered in such a manner that the paper sheet is pulled from the both sides thereof in the delivery direction, thereby preventing the paper sheet from being creased.
A method is also known in which the pressure at the contact portion formed by a pair of fixing members is adjusted so as to be higher at the both ends and lower at the center. When both of the fixing members are roll-type fixing members, distribution of the pressure at the contact part can be controlled by the outer diameter (shape) of the rolls, and when one of the fixing members is a belt-type fixing member, distribution of the pressure can be controlled by the shape of a pressing member (pad) that presses the belt to the other roll-type fixing member.
In this method, the speed of delivering the recording paper sheet at the both edge parts becomes higher than that at the center, similarly to the case described above, and the recording paper sheet is delivered while being pulled from the both sides, thereby preventing the paper sheet from being creased.